Pressure atomization of liquid fuels is known from heating and motor vehicle technology. The efficiency of the combustion depends, in addition to other parameters such as the droplet size of the fuel mist produced on an adequate supply of oxygen being available for the combustion process. The air feed to the flame, however, is fundamentally limited by the nitrogen sheath forming around the flame, isolating the flame region to a certain degree.
An atomizer nozzle and a process for the ultrasonic atomization of liquid fuel that are similar to the arrangement and the process according to claims 1 and 18, respectively, are known from the U.S. Pat. No. 3,977,604. A disc-shaped ultrasonic oscillator is used therein for improving the atomization and the combustion efficiency. The disc-shaped oscillator is arranged in a cloud chamber, spaced from the inner wall of the same. At its bottom the cloud chamber has an outlet with an annular ultrasonic oscillator. The fuel fed centrally to the disc-shaped oscillator is atomized at its upper face, so that a fuel mist is produced, leaving the cloud chamber at its bottom via the outlet and a main nozzle attached thereto.
The ultrasonic atomization has certain advantages over the conventional pressure atomization. The fuel mist distinguishes itself by a smaller average droplet size. The fuel feed can take place via a dosing pump working at normal pressure, which is substantially simpler and less expensive than the high-pressure pump with pressure regulator necessary in a pressure atomizer. Finally, the droplet size can be adjusted via the frequency of the ultrasonic oscillator as a function of the viscosity of the fuel (special edition of `Keramische Zeitschrift` (29) No. 1/1977 "Flussigkeitszerstaubung mit piezokeramischen Ultraschall-Schwingern" (Atomization of Liquids using Piezoceramic Ultrasonic Oscillators)).
As in ordinary pressure atomization, the combustion efficiency in the use of ultrasonic atomizers is also limited in that the combustion, i.e. the flame cone, can not be supplied with an adequate quantity of air or oxygen.